Electrolytic polishing apparatus



Nov. 4, 1952 JJF, KREML 2,616,845

ELECTROLYTIC POLISHING APPARATUS Filed Feb. 10, 1948 INVENTOR- JOHN F. KREML HIS ATTORNEY tice of my invention, I electrolytically polish batches of any of a wide variety of stainless steel products or articles, such as bolts, nuts, washers, screws, rivets, or the like, with the batch or batches immersed in an electrolytic bath preferably comprising substantial amounts both of glycolic acid and sulphuric acid and at least some water. For retaining the several stainless steel products and holding the same collectively immersed for treatment, I provide a support preferably having a, substantially fiat, riddled bottom, and make this bottom, and consequently the products retained thereon, the anode of the electrolytic polishing bath. The openings in the riddled bottom importantly assure admission of the electro-polishing solution to the work and circulation of this fluid at the point of polishing, all contributing to a more efiective polish. Any of the glycolic acid, sulphuric acid electrolytes disclosed in my copending application, Serial No. 724,912, filed January 28, 1947, for example, are satisfactorily used for present purposes.

a The work support which I employ, advantageously takes the form of an electrolytic polishing rack l (see Figures 1 and 2) wherein a shallow riddled pan or tray ll having a flat bottom I la, and perforated raised s-i-des llb, and preferably made of copper or copper-base alloy sheet, is the product supporting anode. The copper, as used, I find not only is a good conductor of electricity, but is especially resistant to electrochemical effects in certain electrolytes and particularly in the glycolic acid-sulphuric acid bath already mentioned. I therefore prefer copper in one form or another for increased rack life. Of course, I sometimes use anodes of other metals or materials without copper, providing they are satisfactory conductors of electricity and are appreciably resistant to attack and effects in the electrolytic polishing media. Sometimes, I mask the underside of the anode, or for that matter all but the article-contact surface of this electrode, with stop-off lacquer, thus to afford greater resistance to the electrolyte and the electropolishing efiect, and to achieve prolonged life of the rack.

An electrical lead I 2 illustratively connects the anode to a suitable source of electrical supply. At times, the anode which I provide is without the sides Ilb and, for example, is only a perforated flat metal piece serving the function of the bottom Ma. The inclusion of sides I lb, however, is preferred, especially when small stainless steel parts are to be electropolished. The perforations importantly are smaller than the stainless steel pieces to be electropolished, and have close enough spacing and frequency to permit ready access of the polishing solution to the work. These holes usually also tend to keep the work pieces separated, from each other, a helpful function toward ensuring uniform polish. Where, for example, small screws or bolts are to be treated on the tray, the holes .illustratively are round and A; inch wide spaced on. inch centers. The size of spacing of the holes,however, is not extremely critical and thus may differ within reasonable limits even for a given size of work.

I usually provide the rack l0 with a cathode, this illustratively being a stainless steel sheet l3 supported an effective distance from the anode. such as directly over the same, and preferably having sieve-like openings 13a. In one embodiment, the cathode I3 simply is an open mesh of stiff or reasonably rigid expanded metal sheet fixed above the anode pan ll, there presenting mesh openings which are appreciably larger than the size of the work. The cathode openings accordingly allow free ingress and egress of the stainless steel work pieces, assist the distribution of these articles over the anode pan, and encourage unrestricted flow of the polishing solution. Yet, to promote better electrical activity between the electrodes during my polishing treatment, the cathode openings preferably are as small as is consistent with free ingress and egress of the work pieces. In general, the cathode is as close to the anode as considera tions of work piece size and good electro-functioning permit. Usually, about /2 inch to 2 inch spacing of the electrodes is satisfactory for most small articles treated. The anode and cathode conveniently are electrically insulated from each other by any one of a number of non-conducting materials, such as wood, Bakelite, quartz porcelain, or the like. For example, I employ spaced insulating posts [4 for this purpose, these interconnecting the outer extremities of the anode and cathode.

The rack I0 has a lead l5 extending from the cathode for connection with a suitable source of electrical power. This lead, and the anode lead [2 for example, are heavy bars which conveniently have hooks 12a, and |5a or other fastening means, for suspending the rack in the polishing bath, as from electrical terminals I! and [8, both of the latter illustratively being rigidly secured to the polishing vat l9 (see Figure 2), or, for example, suitably supported to travel with the rack along the vat walls during the polishin operations.

In employing the rack such as for the polishing of a batch of stainless steel screws, I usually dump the articles from a bag, conveyer, or from a scoop, onto the top of the cathode l3 before immersing the rack in the polishing bath. These articles sift through the openings [3a of the oathode and fall onto the top surface of the anode bottom Ila, there scattering and some rolling and lodging at the head in the anode perforations Hc against further movement. In certain instances, I subject the rack to a light bouncing or shaking operation to achieve passage through the cathode or to spread or relieve stacking of the articles on the anode. The screws illustratively cover substantially the entire product supporting area of the anode, there establishing goo-d electrical contact. Some touch each other and in many instances remain on top of, or crossed over, others.

I then immerse the rack including the anode and cathode and the supported screws l6 into a glycolic acid, sulphuric'acid electrolyte 20, in the polishing vat l9, this solution illustratively containing, by weight, about 20% to glycolic acid, 10% to 60% sulphuric acid, and 2% to 35% water.

Lead hooks In and lid, with the rack immersed. fit in proper relation upon the corresponding electrical terminals I! and It, thus establishing electrical connection for the polishing treatment. Upon energizing the vat terminals from electrical supply, the electrolytic polishing operation begins.

treatment involves the electrolytic removal of an The temperature'con ditions of the glycolic acid, sulphuric acid elecextremely thin layer of metal from the immersed product surfaces. During this action, I avoid breaking the electrical connections or contact of the screws with the anode. A substantially continuous electrical connection I find assures a more uniform polish. When the contact is interrupted it seems that an oxide film is formed at the point of contact which thereafter results in poor conductivity and subsequent poor polishing. Continued contact in my method and apparatus is encouraged by the holes in the anode pan, which help lodge the screws. Both electrodes while exerting their electrical functions, in being open or perforated assist circulation and effectiveness of the polishing fluid and avoid entrapment of gas which might cut down the prevailing current density. Good throwing power is achieved.

After a time period of about minute to 5 minutes, for example, I shut off the electrolytic treating current and withdraw the rack from the bath. I find it convenient to rinse the rack with the polished screws in clear water. Thereafter, I dump the batch into a suitable receptacle or the like such as by inverting the rack. My electrolytically polished stainless steel products thus are illustratively achieved.

The electrolytic polishing process which I provide is economical and capable of being carried out under operating conditions which are easy to control as during the expeditious mass production of stainless steel articles of outstanding sur face quality. The batch-polished stainless steel articles achieved are substantially uniform from product to product of the batch, and are substantially free of etching, burns, and blemishes. Further, the electrolytic polishing apparatus which I provide is easily operated and facilitates the handling of a plurality of articles to the end of achieving a thoroughly satisfactory polish.

Thus it will be seen that in this invention there are provided an electrochemical process and apparatus for electrolytically polishing metal articles in which the various objects hereinbefore noted together with many thoroughly practical advantages are successfully achieved. It will be seen that both the method and apparatus contribute to successful batch-polishing of articles and call for minimum attention to the individual components of the batch.

While my invention has been described as being particularly useful for the electrochemical treatment of stainless steel articles, it will be understood that I also employ my method and apparatus in conditioningor polishing a wide variety of other products, among these being aluminum, nichrome and inconel.

It will also be understood that while I regard glycolic acid, sulphur acid electrolytes as being especially beneficial in conjunction with the use of my method and apparatus for polishing of stainless steel and other metals, I sometimes use other acid electrolytes such as a solution containing citric acid and sulphuric acid, or a solution containing phosphoric acid and sulphuric acid, in the electrolytic polishing treatment or with the apparatus.

Also, it will be appreciated that while my electrolytic polishing apparatus may take the form of a rack such as described hereinbefore, or even a plurality of racks stacked one above or beside the other, my anode-cathode arrangement and features of providing the same in perforated condition at times are embodied in other physical an endless conveyer-anode, beneath a fixed cathode, to achieve the polishing function.

As many possible embodiments may be made of my invention and as many changes may be made in the embodiment hereinbefore set forth, it will be understood that all matter described herein is to be interpreted as illustrative and not as a limitation.

I claim:

1. Electrolytic polishing apparatus for toploading comprising, in combination, fiat anode means for supporting a batch of products to be polished and having openings therein smaller than the individual products, cooperating fiat open mesh cathode means above the anode and having openings therein of suflicient size to ad mit the products to the anode when charged onto the cathode, electrical insulating spacers fixedly secured to said anode and to said cathode and maintaining said open mesh cathode at effective electrolytic polishing distance above the product supporting zone of the anode, an electrolytic polishing solution, a container therefor, and means supporting said anode and cathode in substantially horizontal position in said solution.

2. An electrolytic polishing rack for top-loading comprising, in combination, fiat tray-anode means for supporting a batch of products in electrolytic polishing position and having openings therein smaller than the individual products but sufficiently large for the products to partially lodge therein and give firm electrical contact, a cooperating fiat open mesh cathode above the anode and having openings therein of suflicient size to admit the products to the polishing position on the anode when charged onto the cathode, and electrically insulating posts fixedly secured to said anode and to said cathode and uniformly maintaining said cathode at effective electrolytic polishin distance over the product supporting zone of said anode.

3. An electrolytic polishing assembly for toploading comprising, in combination, fiat anode means for supporting a batch of products and having openings therein smaller than the individual products, cooperating flat open mesh cathode means above the anode and having openings therein of sufficient size to admit the prodnets to the anode when charged onto the cathode, electrical insulating spacers fixedly secured to said anode and to said cathode and maintaining said open mesh cathode at effective electrolytic polishing distance above the product supporting zone of the anode, and electrically conductive means, one secured to the anode means and the other to the cathode means for supporting the same in substantially horizontal position.

JOHN F. KREML.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 574,038 Marks Dec. 29, 1896 615,699 Hartley et al. Dec. 13, 1898 742,131 Pratt Oct. 20, 1903 1,963,363 Hale June 19, 1934 2,390,282 Tour et al Dec. 4, 1945 OTHER REFERENCES Plating Rack Manual, by Belke, Published in 1947 by Belke Mfg. Co., Chicago, Illinois, pages arrangements, such as an arrangement involving 51 and 99. 

1. ELECTROLYTIC POLISHING APPARATUS FOR TOPLOADING COMPRISING, IN COMBINATION, FLAT ANODE MEANS FOR SUPPORTING A BATCH OF PRODUCTS TO BE POLISHED AND HAVING OPENINGS THEREIN SMALLER THAN THE INDIVIDUALS PRODUCTS, COOPERATING FLAT OPEN MESH CATHODE MEANS ABOVE THE ANODE AND HAVING OPENINGS THEREIN OF SUFFICIENT SIZE TO ADMIT THE PRODUCTS TO THE ANODE WHEN CHARGED ONTO THE CATHODE, ELECTRICAL INSULATING SPACERS FIXEDLY SECURED TO SAID ANODE AND TO SAID CATHODE AND MAINTAINING SAID OPEN MESH CATHODE AT EFFEC- 